help with php5 and mysql on ubuntu lamp.

[meomike2000]

i have been using php for a short while now and am starting to add on mysql database.
i have been reading a book about using php and mysql together and i have a sample script from that book that i have linked from my home page.
when i click on the link i get this error:

Fatal error: Call to undefined function mysql_connect() in /home/mike/Desktop/web/testdatabase.php on line 7

lines 6, 7, and 8 of my code is:

//open connection to database server.
$connection = mysql_connect('localhost', 'directory', 'directory')
or die ('unable to connect!');

the server is mine (ubuntu8.04 with php5) and this is not actually on the net, just my local machine.
as i am new to this and the book dont say anything about this "function" i could use a little help.

thanks in advance mike......